Preparation of unsaturated compounds by xanthate decomposition

ABSTRACT

Simple and complex unsaturated compounds are prepared by decomposition of certain xanthate esters, Xanthate esters of the form: WHERE R is an alkyl function having at least one H in a position alpha to the R - O bond, (C)n is a linear alkyl function either substituted or unsubstituted, with n 1 - 3, X has a basicity greater than the FUNCTION AND COMPRISES A C or S containing functional group having at least one double or triple bond to a hetero atom, the functional group being connected to (C)n through C or S; will decompose upon heating in water or in a protonated non-aqueous solvent, e.g. methanol, ethanol, etc., glycol, cellosolve, liquid ammonia, pyridine, lower alkyl amines, aniline, etc., to yield an unsaturated derivative of R.

atent United States Burke et al.

[ 1 May 30, 1972 [72] Inventors: Noel I. Burke, Danville; Douglas J.Bridgeford, Champaign; Albin F. Turbak, Danville, all of Ill.

[73] Assignee: Tee-Pak, Inc., Chicago, lll.

[22] Filed: Sept. 10, 1969 [21] Appl. No.: 856,813

[52] 11.5. CI. ..260/91.3 VA, 260/88.l R, 260/94.1, 260/216, 260/2335,260/397.2, 260/682 [51] Int. Cl. ..C08f 3/34, C08f 23/00, C08f 27/00[58] Field of Search ..260/88.1, 91.3 PV, 91.3 VA, 260/94.1, 212, 218,233.5, 682, 397.2, 88.1 R, 216

[56] References Cited UNlTED STATES PATENTS 2,041,907 5/1936 Dosne..18/54 2,852,333 9/1958 Cox et a1 ..18/54 2,751,628 6/1956 Car enter etal. .....l8/55 2,838,469 6/1958 Buselli et a]. ..260/45.5

Primary Examiner-Joseph L. Schofer Assistant ExaminerStanford M. LevinAttorney-Neal J. Mosely and David V. Munnis [57] ABSTRACT Simple andcomplex unsaturated compounds are prepared by decomposition of certainxanthate esters,

Xanthate esters of the fonn:

where R is an alkyl function having at least one H in a position alphato the R-O bond, (C), is a linear alkyl function either substituted orunsubstituted, with n= l 3, X has a basicity greater than the- C= Sfunction and com prises a C or S containing functional group having atleast one double or triple bond to a hetero atom, the functional groupbeing connected to (C), through C or S; will decompose upon heating inwater or in a protonated nonaqueous solvent, e.g. methanol, ethanol,etc., glycol, cellosolve, liquid ammonia, pyridine, lower alkyl amines,aniline, etc., to yield an unsaturated derivative of R.

9 Claims, No Drawings PREPARATION OF UNSATURATED CONIPOUNDS BY XANTHATEDECOMPOSITION BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION Thisinvention relates to an improved process for the preparation ofunsaturated compounds from alcohols by thermal decomposition of certainxanthate ester intermediates.

2. DESCRIPTION OF THE PRIOR ART The production of unsaturated compoundsfrom alcohols has been known for a long time. However, most of themethods of dehydration involve the treatment of the alcohol with astrong acid or the thermal decomposition of the alcohol or one of itsderivatives. Some of the better known and most often used methods ofdehydration are the use of an acid such as sulfuric acid, phosphoruspentoxide, phosphorus oxychloride, and other strong acids; the pyrolysisof the alcohol on alumina, the pyrolysis of an ester of the alcohol,usually the acetate or benzoate, and the pyrolysis of a xanthate esterof the alcohol. Not all compounds will survive the treatment of a strongacid and-or pyrolysis. Polymeric alcohols as a class will usuallydecompose to a black, often tarry mass if a strong acid or thermaldecomposition technique is used in an attempt to produce an unsaturatedcompound from the alcohol.

The Chugaev reaction prepares certain unsaturated compounds by pyrolysisof alkyl xanthate esters. This reaction is run anhydrous at a hightemperature and is applicable only to the production of a limited numberof unsaturated compounds.

Recently, Rogovin has produced an unsaturated cellulose by making thetosylate, displacing the tosylate with iodide, and finallydehydrohalogenating the iodide derivative. Unlike previous attempts todehydrate cellulose by pyrolitic-means, the Rogovin procedure gave awhite unsaturated cellulose with a double bond in the C C position.While the Rogovin procedure gives a pure product, the cost of thereagents involved makes the economic practicality of the procedure quitedoubtful.

SUMMARY OF THE INVENTION This invention was based upon the discoverythat simple and complex, monomeric and polymeric, unsaturated compoundsmay be prepared by decomposition of certain xanthate esters.

Xanthate esters of the form:

where R is an alkyl function having at least one H in a position alphato the R 0 bond, (C), is a linear alkyl function either substituted orunsubstituted, with n l 3, X has a basicity greater than the functionand comprises a C or S containing functional group having at least onedouble or triple bond to a hetero atom, the functional group beingconnected to (C),, through C or S; will decompose upon heating in wateror in a protonated nonaqueous solvent, e.g. methanol, ethanol, etc.,glycol, cellosolve, liquid ammonia, pyridine, lower alkyl amines,aniline, etc., to yield an unsaturated derivative of R. The term alkylfunction" as used above refers to a functional group which is alkyl instructure which may be complete in itself or may be substituted or maybe a part of a larger molecule or functional group. The alkyl function Rmay be a simple or complex, substituted or unsubstituted, monomeric orpolymeric, function but must have at least one H in a position alpha tothe R 0 bond. (C),, is an alkyl function of the form, CR CR CR, or CR'CR CR where R, R and R may be hydrogen or inert substituents.

The decomposition of xanthate esters in accordance with this inventionis preferably carried out in water or in a protonated non-aqueoussolvent, preferably acidified to a hydrogen activity, (defined as log ofeffective hydrogen ion concentration) of about 3 6. When the xanthatedecomposition is carried out in water it is preferred to heat a solutionor slurry of the xanthate in water at a pH in the range of about 4 Thisinvention arose as a result of work done on certain cellulose xanthatederivatives and an effort to establish a mechanism for the decompositionof xanthates. The work which we carried out appears to support themechanism which we have proposed and which is described herein for abetter understanding of the invention. The proposed mechanism howevermerely represents our best current theory of the mechanism of thereaction and should not be considered to be a completely accuratedescription of the way that the reaction takes place.

During the course of some work on cellulose xanthate derivatives, weattempted to determine the reason that cellulose xanthate S-propanesulfonate, which is water soluble, would not wash off fabrics that had a2 4 percent addon of the polymer. This investigation showed that atleast part of the sulfur in the derivative was being lost upon heating,both on the fabric and in solution. Since cellulose xanthate derivativesare extremely complex we decided that at least the early part of theinvestigation should be done on simple model compounds.

The isopropyl xanthate S-propane sulfonate derivative was prepared, thendissolved in water at pH 4.5 and the solution heated at C. The gasesevolved were examined using gas chromatography. The gases that wereexpected from hydrolysis, viz. carbon disulfide, carbonyl sulfide,carbon dioxide, hydrogen sulfide, and in some cases sulfur dioxide, werefound as well as an unidentified gas. Due to the long retention time ofthis gas it was thought to be an organic material. A sample of the gaswas collected and identified by infrared spectroscopy as propylene. Thepresence of propylene in the evolved gases was totally unexpected inview of previous conceptions of the mechanism of the xanthatedecomposition.

In order to be sure of the presence and the approximate amount ofpropylene, the decomposition was repeated, but the evolved gases wereseparated and the hydrocarbon passed into bromine in carbontetrachloride. The excess bromine was back titrated and the organicportion was removed and the carbon tetrachloride evaporated to leave anoil. The infrared spectrum of this material was identical with theinfrared spectra of an authentic sample of dibromopropane. It wasthought at first that the reaction might be similar to the well knownChugaev reaction which utilizes alkyl esters of xanthates in pyrolysis.However, the Chugaev reaction is run anhydrous at a high temperature.Nevertheless, S-methyl-Z-propyl xanthate was prepared and decomposed inaqueous media at pH 4.5. This yielded only minute amounts of propylene.

Since the decomposition did not seem to be a modification of the Chugaevreaction and since there is no precedent for this reaction in theliterature, a variety of xanthate derivatives were prepared in anattempt to determine the utility and scope of the reaction.

The electron withdrawing power of the attached group was considerednecessary for the decomposition reaction. Therefore, the carboxy methylgroup was prepared and decomposed over a range of pH. The pH range of 45 seems to give the best result. At pH 4.5 the reaction is relativelyslow for many derivatives but gave good yields if carried out for a longenough time.

In the investigation, various derivatives were prepared of xanthates ofn-propanol, 2-propanol, 2-butanol, cyclohexanol and cholesterol. Thederivatives used included esters of the alcohol xanthates prepared fromderivatives of 2-propanone, acetaldehyde dialkyl acetal, cyanoethyl andcyanomethyl. The decomposition of each of these derivatives seems to bea critical function of the pH of the media if a reasonable yield is tobe obtained. It seemed possible that the pH dependence of the reactionwas due to competing reactions. The primarily competing reaction thatwould reduce the yield is hydrolysis. At low pH, the hydrolysis ofxanthate esters is acid-catalyzed and at high pH of the hydrolysis isbase catalyzed. If the rate dependent step of the decomposition toproduce an unsaturated compound is a steric one, that is, the moleculemust be in a particular configuration, then the pH dependence is one ofreduction of by-products and does not directly affect the rate ofdecomposition. Since the time of these reactions is generally quitelong, it is reasonable that hydrolysis must be repressed if thedecomposition to an unsaturated product is to take place.

With the pH dependence inmind and the apparent necessity for thepresence of an electron withdrawing group, the following mechanism isproposed:

, form. The unsatisfied valences on the carbon atoms are considered tobe connected to hydrogen, hydrocarbon radicals, or any inert substituentor functional group.

The postulated mechanism would also be applicable to the formation of asix membered ring as the transitory intermediate. This mechanismindicates that it is not the electron withdrawing power of the attachedgroup, but the ability of the group to produce a carbonium ion on thecarbon atom containing the group. Thus, a nitroethane ester would not beexpected to give any unsaturated product. When the nitroethanederivative of isopropyl xanthate was treated for 150 hours no propylenewas obtained.

The proposed mechanism also indicates that any atom in the intermediatethat is able to support a positive charge would probably not undergo thedecomposition. The types of derivatives that the mechanism predicts thatwould not undergo the decomposition are the dithiocarbamates and amidederivatives among others.

When dithiocarbamate esters were treated they all failed to give thecorresponding unsaturated compounds. Likewise,

amide derivatives of xanthates failed to undergo the decomposition, aspredicted.

in the case of the amides, the protonated carbonyl would be the moststable form of the ion and in the case of dithiocarbamates the chargewould be relatively stable on the nitrogen; however, this intermediatecould easily add water to give the amine that was used to prepare thedithiocarbamate.

The proposed mechanism would indicate that any molecule that can obtainthe required steric configuration and conforms to the formula givenabove (in the abstract of the disclosure) will yield the correspondingunsaturated compound on decomposition. The sulfonate group does not fitthe same mechanism as the other formulae; however, this group was theonly one that gave sulfur dioxide in the gas chromatographic analysis ofevolved gases. A mechanism for decomposition of the sulfonate derivativeinvolves the formation of a six membered hetero cycle containing sulfur,as an intermediate, with an accompanying splitting off of sulfurousacid, which decomposes to yield sulfur dioxide. The heterocyclicintermediate decomposes to yield the desired unsaturated compound.

DESCRIPTION OF THE PREFERRED EMBODIMENTS in the following examples thereare illustrated a variety of starting materials and reaction conditionswhich illustrate the general operability of our invention as describedbroadly above. The examples illustrate the general preparation ofolefins by thermal decomposition of certain xanthate esters in aqueousmedia or in other protonated solvents, preferably at a hydrogen activityin the range of about 3 6.

EXAMPLES l 17 A series of experiments were carried out in which variousxanthate derivatives were decomposed under the conditions of thisinvention to produce unsaturated compounds. In each of the examples, 10m moles of the xanthate derivative were dissolved in 15 ml. of water andthe pH adjusted to the desired value with acid or alkali. The solutionswere then heated under reflux for the indicated time. The reaction canbe carried out at lower temperatures but longer reaction times arerequired. Nitrogen was used as a carrier gas at 30 cc/min. to removegaseous products. The nitrogen effluent was passed through a solution ofcopper acetate to remove any hydrogen sulfide that might be evolved andthen through a 0.5N NaOH to remove carbon dioxide and any gas that mightpass the copper trap. Finally the nitrogen was passed into carbontetrachloride, usually containing bromine, at 30 C. Most of the yieldswere calculated by backtitration of the bromine that had been added. Ablank was run to determine the loss of bromine from the trap (which wasnil at the longest time used). All of the unsaturated products producedwere isolated pure at least once and identified by gas chromatographyand infrared spectroscopy.

In Table 1 below the results of Examples 1 17 are tabulated, indicatingthe reactant xanthate compound, pH of the decomposition system, reactiontime, yield (in percent based on the reactant), and the unsaturatedproduct produced.

TABLE I Time of Example reaction, Yield, number Xanthate reactant pllhours percent Product l S-(3-propane sulfonatO-Z-propyl mutate (sodiumsalt) 5.0 24 3G Propylene. 2.. d0.. 1.5 50 8 D0. 3 S-(B-propanesulfonate)-2-bu ithate (sodium salt) 5. 6 5O 16 Bulsylencv 4. "do 5.5 5018 o. 5. S-methyl-2propyl xsnthate t 4. 0 3 PropyleneS-carboxyrnethyl-2-propyl xanthate (so um salt) 4. 5 24 27 Do. 7". d04.5 84 73 D0. 8.. d0 4.5 154 D0. EL t ..do 8.5 50 11 Do. 10 r "do r t tt l." 50 12 Do. 1 ScarboxymethyH-gropyl xanthatc (sodium salt) 4. 5 2422 Do. 1 S-mrhoxymethyl-2- utyl xanthnte. we. t 4. 5 50 48 Butylene. 1'Scyanoethyl cyclohexyl xanthate 4. 5 50 65 Cyelohexeno. l4 S-ethylearboxyinethylate cyclohexyl xanthate 4. 5 45 Q, 15. S-(2-propanouecyclohexyl xantliate 4. 5 I00 40 D 16 S-cyanocthyl chloesterol xanthate.a H 4.3 96 59 A cholestradiene. l7. S-(neetaldehydv dimethyl acvtal)cholesterol xanthate 4.3 48 33 D0.

1 (hngaov control base pt. run.

The xanthate ester reactants used in the above examples are largelyknown compounds which may be made by known procedures. The preparationof the xanthate esters used above was by mixture of the xanthate sodiumsalt and the reactant used for forming the derivative in solution or ina slurry, usually in the same alcohol from which the xanthate wasderived. The xanthate salt and derivative were added in equal molarportions to the solvent and the reaction generally was highly exothermicand went to completion in a very short time. The reactants and thesolvent used in preparing the xanthate esters for the various examplesin the table are as follows:

DECOMPOSITION OF XANTHATES IN PROTONATED SOLVENTS The following examplesillustrate the decomposition of various xanthate esters in protonatednon-aqueous solvents.

EXAMPLE 18 S-( 3-propane sulfonate)-2 propyl xanthate is added tomethanol and acidified to a hydrogen activity of 5. The solution isrefluxed for about 24 hours with a substantial evolution of propylene.

EXAMPLE l9 S-(3-propane sulfonate)-2-butyl xanthate is dissolved inethanol acidified to a hydrogen activity of 5.5. The solution isrefluxed for a period of about 48 hours with a substantial evolution ofbutylene.

EXAMPLE 2O S-carboxymethyl-Z-propyl xanthate is dissolved in ethyleneglycol and acidified with HCl to a hydrogen activity of 4.5. Thesolution is heated to 100 C. for about 24 hours with a substantialevolution of propylene.

EXAMPLE 21 S-carboxymethyl-Z-butyl xanthate is mixed with pyridine andacidified to a hydrogen activity of 4.5 by addition of pyridinehydrochloride. The mixture is heated to reflux and butylene is slowlyevolved over a period of about 40 hours.

EXAMPLE 22 S-(2-propanone) cyclohexyl xanthate is mixed withcyclohexanol and acidified to a hydrogen activity of 4 with HCl. Themixture is heated at reflux for a period of about 90 hours with asubstantial formation of cyclohexene.

DECOMPOSITION OF POLYMERIC ALCOHOL XANTHATE ESTERS Various polymericalcohol xanthate esters were prepared from polymeric alcohols such ascellulose, starch, amylose, and polyvinyl alcohol. The sodium xanthatesalts were prepared by conventional xanthation methods. The sodiumxanthate salts were dissolved in water and reacted in equal molarproportions (with respect to-the xanthate group) with various reactantsto produce the desired ester derivatives for subsequent decomposition.The reactions in each case were exothermic and went to substantialcompletion in a very short time.

Polymeric alcohol derivatives, prepared as described above, wereslurried or dissolved in water at a concentration of 5 10 percent. Theslurry was adjusted in pH to the desired value by addition of acid orbase and refluxed for an extended period of time. The polymers were thenfiltered, washed in water, methanol and either acetone or methylenechloride and dried under vacuum (28 in. Hg.) at room temperature. Thepolymers were then slurried in methylene chloride or carbontetrachloride and an excess of bromine was added and the slurriesstirred overnight. The polymers were then filtered, washed withmethanol, water, and acetone to remove excess bromine and chlorinatedsolvents, then dried at room temperature in a vacuum oven (28 in. Hg.)to a constant weight. As a control, each of the polymers was regeneratedfrom its xanthate by use of acid, washed to remove by-products and thentreated in the same manner as the derivatives. In no case did theregenerated polymers show any bromine, indicating that the polymers donot have any'unsaturation.

EXAMPLE 2 3 Sodium cellulose xanthate was reacted in aqueous suspensionwith sodium chloracetate to yield the carboxymethyl ester of cellulosexanthate. The carboxymethyl ester of cellulose xanthate was thenslurried in water at a concentration of about 5 percent and the pHadjusted to 8.5. The slurry was heated at reflux for about 60 hours.After the polymer was worked up in accordance with the above-describedprocedure, it was found that there had been a yield of 39 percentunsaturated cellulose derivative. In the cellulose derivative theunsaturation is present both as the vinyl unsaturation, i.e. in the 6position, and as ring unsaturation.

The same procedure was repeated except that the carboxymethyl ester ofcellulose xanthate was decomposed by reflex in 4.5 pH aqueous slurry.After 72 hoursreaction time there was obtained a 63 percent yield ofunsaturated cellulose.

When the same procedure of repeated with the substitution of methanol orethanol as the decomposition medium a similar result is obtainedprovided that the solvent or reaction medium is protonated by additionof sufiicient l-lCl to produce a hydrogen activity of about 4 5.

EXAMPLE 24 A 2-propanone derivative of cellulose xanthate was preparedby reacting equal molar quantities of sodium cellulose xanthate andchloracetone in water. The ester derivative was slurried in water at aconcentration of about 10 percent and pH of 5.0. The slurry was heatedto reflux for a period of 24 hours and the polymer worked up asdescribed in the general procedure given above. There was a 42 percentyield of unsaturated cellulose having unsaturation both in the 6position and in the anhydroglucose ring.

When this procedure is repeated and the ester decomposed in methanol orethanol, similar results are obtained, provided that the solvent isprotonated by addition of HO in an amount sufficient to yield a hydrogenactivity of about 4 5.

EXAMPLE 25 .lulose.

A similar result is obtained when the cellulose ester is decomposed inethanol, methanol, ethylene glycol, or cyclohexanol acidified to ahydrogen activity of about 4 5.

Sodium cellulose xanthate was reacted in aqueous solution withchlorocyanomethane to yield the cyanomethyl ester of cellulose xanthate.

The cellulose xanthate ester was slurried at a percent concentration inwater and the pH adjusted to 4.5. The slurry was refluxed for 24 hoursand the polymer worked up as described in the general procedure givenabove. There was an 8.1 percent yield of unsaturated cellulose.

A similar result is obtained when the cellulose xanthate ester isdecomposed by heating in a non-aqueous protonated solvent.

EXAMPLE 27 Sodium starch xanthate was reacted in aqueous solution withacrylonitrile to yield the cyanoethyl ester.

The cyanoethyl starch xanthate was slurried at a 5 percent concentrationin water and pH adjusted to 4.5. The slurry was refluxed for 90 hoursand the polymer worked up as described in the general procedure. Therewas a 29 percent yield of unsaturated starch, with the unsaturationbeing present both in the 6 position and in the anhydroglucose ring.

The decomposition of the starch xanthate ester in a protonated solventyields an unsaturated starch as in the similar decomposition of thecellulose xanthate esters.

EXAMPLE 28 Starch xanthate was reacted in aqueous solution with sodium3-chloropropanate to yield the carboxyethyl ester of starch xanthate.

The starch xanthate ester was then slurried at a 10 percentconcentration in water and the pH adjusted to 4.5. The slurry wasrefluxed for 168 hours and the polymer worked up as described in thegeneral procedure above. There was a 44 percent yield of unsaturatedstarch with the unsaturation being present both in the 6 and ringpositions.

The thermal decomposition of the starch xanthate ester in otherprotonated solvents yields unsaturated starch as the product in goodyield.

EXAMPLE 29 Sodium starch xanthate was reacted in aqueous solution with2-chloro l,l-dimethoxy ethane to yield the acetaldehyde dimethyl acetalester of starch xanthate.

The starch xanthate ester was slurried in waster at pH 4.5 and aconcentration of 5 percent. The slurry was refluxed for 90 hours and thepolymer worked up as described generally above. There was a 5 8 percentyield of unsaturated starch in this process.

When the starch xanthate ester is decomposed in non-aqueous protonatedsolvents unsaturated starch is obtained in good yield.

EXAMPLE 30 Sodium amylose xanthate was reacted in aqueous solution with2-chloro l,l-di-ethoxy ethane to yield the acetaldehyde diethyl acetalester of amylose xanthate.

The amylose xanthate ester was slurried in water at 5 percentconcentration at a pH of 4.5. The slurry was refluxed for 52 hours andthe polymer worked up as described generally above.

There was a 41 percent yield of unsaturated amylose with theunsaturation present both in the 6 position and the ring. Thedecomposition of amylose xanthate ester in other protonated solventsgives similar good yields of unsaturated amylose.

EXAMPLE 3l Sodium polyvinyl alcohol xanthate was reacted with 2- chlorol,l-diethoxy ethane in aqueous solution to yield the acetaldehydediethyl acetal ester.

The polyvinyl alcohol xanthate ester was slurried at a 10 percentconcentration in water and the pH adjusted to 4.5. The slurry wasrefluxed for 6 hours and the polymer worked up as described in thegeneral procedure above.

There was a 26 percent yield of a vinyl alcohol-acetylene copolymerwhich is the theoretical derivative of a partial dehydration ofpolyvinyl alcohol. A similar yield of vinyl alcohol acetylene copolymeris obtained when polyvinyl alcohol xanthate esters are decomposed inother protonated solvents at a suitable hydrogen activity.

The relative proportion of vinyl alcohol and acetylene in the copolymerproduced in this example is dependent on a variety of factors. The useof a suitably high D. S. polyvinyl alcohol and carefully selectedxanthation conditions to yield essentially 1.60 D.S. xanthate will yieldan acetylene vinyl alcohol copolymer which approaches nearly percentpolyacetylene in composition.

EXAMPLE 32 A vinyl alcohol acetylene copolymer, produced as described inExample 31, is treated with aqueous alkali and CS to yield the xanthatederivative. The sodium xanthate derivative of the vinyl alcoholacetylene copolymer is then reacted in aqueous solution with 2-chlorol,l-diethoxy ethane to yield the acetaldehyde diethyl acetal ester.

This xanthate ester of the vinyl alcohol acetylene copolymer is slurriedin water at pH 4.5 and a concentration of 10 percent. The solution isrefluxed for 100 hours to yield a vinyl alcohol acetylene copolymerhaving a substantially higher acetylene content. The product of thisreaction is then re-xanthated and the ester derivative again formed anddecomposed. After 3 or 4 successive xanthations and de xanthations theproduct obtained is almost 100 percent polyacetylene. The product isessentially pure polyacetylene (pure with respect to the presence ofcopolymer) containing small amounts of reaction by-products. Theproperties of polyacetylene are dependent upon the DR of the polyvinylalcohol from which it was derived and also the steric configuration ofthe polyvinyl alcohol. Thus, polyacetylene varies in physical propertiesfrom an oily liquid at low DP. (and at higher D.P.s in the case ofhighly branched structures) to a waxy solid at high DP. (and especiallyin a linear configuration). The polymer has substantial electricalconductivity as compared to other organic compounds and absorbssubstantial amounts of bromine readily. Polyacetylene is useful for avariety of purposes for which other polymers are used. It is useful as acoating material and as a structural plastic in the form of a sheet orfilm or molded article. The polymer may be brominated to yield aderivative which is highly flame resistant.

From the foregoing examples, we have demonstrated that a variety ofsimple and complex unsaturated compounds can be prepared bydecomposition of certain xanthate esters. We have shown that xarrthateesters of the form:

substituted or unsubstituted, with n l 3, X has a basicity greater thanthe function and comprises a C or S containing functional group havingat least one double or triple bond to a hetero atom, the

functional group being connected to (C),, through C or S; will decomposeupon heating in water or in a protonated nonaqueous solvent e.g.methanol, ethanol, etc., glycol, cellosolve, liquid ammonia, pyridine,lower alkyl amines, aniline, etc., to yield an unsaturated derivative ofR.

In the xanthate esters which are decomposed in accordance with thisinvention the R group in the formula given is a simple or complex,substituted or unsubstituted, monomeric or polymeric, alkyl functionhaving at least one H in a position alpha to the R bond. We have shownthat the R group may be a simple alkyl group or may be a highly complexpolymer and may contain substituents of any and all kinds so long asthey are inert under the conditions of preparation and decomposition ofthe xanthate ester. The X group may be any of a variety of functionalgroups limited only in that it has a basicity greater than thethiocarbonyl function. Typical examples of the X group include thefollowing:

We claim: 1. A method of preparing unsaturated compounds which comprisesheating a xanthate ester of the formula where R is an alkyl functionhaving at least one H in a position alpha to the R 0 bond, (C), is alinear alkyl function either substituted or unsubstituted, with n l 3, Xhas a basicity greater than the function and comprises a C or Scontaining functional group having at least one double or triple bond toa hetero atom, the functional group being connected to (C) through C orS; in water at an acidic pH or a protonated non-aqueous solvent to yieldan unsaturated derivative of R.

2. A method in accordance with claim 1 in which R is alkyl orcycloalkyl, either unsubstituted or containing inert substituents.

3. A method in accordance with claim 1 in which R is polymeric.

4. A method in accordance with claim 1 in which R is a constituent groupin cellulose, starch, amylose, or polyvinyl alcohol.

5. A method in accordance with claim 1 in which the xanthate ester isdecomposed by heating in water at an acidic pH or a protonated non-aqueous solvent at a hydrogen activity of about 3 6.

6. A method in accordance with claim 1 in which X is and the unsaturatedproduct is olyacetylene or a copolymer of vinyl alcohol and acetyleneaving a higher polyacetylene content than the initial reactant.

9. Copolymers of vinyl alcohol and acetylene.

* k I t t

2. A method in accordance with claim 1 in which R is alkyl orcycloalkyl, either unsubstituted or containing inert substituents.
 3. Amethod in accordance with claim 1 in which R is polymeric.
 4. A methodin accordance with claim 1 in which R is a constituent group incellulose, starch, amylose, or polyvinyl alcohol.
 5. A method inaccordance with claim 1 in which the xanthate ester is decomposed byheating in water at an acidic pH or a protonated non-aqueous solvent ata hydrogen activity of about 3 -
 6. 6. A method in accordance with claim1 in which X is
 7. A method in accordance with claim 1 in which R is aconstituent group in polyvinyl alcohol and the unsaturated product ispolyacetylene or a copolymer of acetylene and vinyl alcohol.
 8. A methodin accordance with claim 1 in which R is a constituent group in acopolymer of vinyl alcohol and acetylene and the unsaturated product ispolyacetylene or a copolymer of vinyl alcohol and acetylene having ahigher polyacetylene content than the initial reactant.
 9. Copolymers ofvinyl alcohol and acetylene.